The research detailed in this application for the coming grant year concerns itself principally with mechanisms of cellular immunity. A protein isolated from the sea star Asterias forbesi, sea star factor (SSF), has been demonstrated to simulate many of the effector substances released from immunized T cells exposed to specific antigen, and may therefore be used as a probe for T-cell function. This protein has a molecular weight of approximately 38,000 daltons and is composed of a single heavy and light chain. While the amino acid content of each of these chains is known, we will now study the sequence of amino acids within both of these chains and compare them with known sequences of vertebrate immunoglobulin chains, Beta 2 microglobulin, and of various of the complement components. We will also study the binding affinity of SSF to cell membranes, including the possible distinction between binding to T cells and B cells. Since recent data demonstrate that the primary response to T-dependent antigens (for example, alloantigen) can be blocked by preexposure of the responding cells to SSF, but not the secondary (anamnestic) response, we will investigate the possibility that suppressor cells are responsible for these disparate findings. The application of SSF to tumor immunity will be studied, using transplantable mouse methylcholanthrene-induced tumors in attempts to investigate possible adjuvant effects when minute quantities of SSF are coupled to tumor cells for specific immunization in syngeneic hosts. BIBLIOGRAPHIC REFERENCES: Inhibition of precytotoxic T cell differentiation in vitro. R.A. Prendergast, N. Gleiner, and C.L. Reinisch, Fed. Proc. 35:473, 1976. Isolation and characterization of sea star factor. R.A. Prendergast and S.H. Liu, Scan. J. Immunol., 1976 (in press).